On the formation of solar wind & switchbacks, and quiet Sun heating

TL;DR

This study compares magnetic and flow properties of quiet Sun and coronal holes to understand solar wind formation, coronal heating, and switchback phenomena, proposing a unified model involving interchange reconnection and magnetic field dynamics.

Contribution

It provides a detailed comparative analysis of chromospheric and transition region lines in QS and CH, linking magnetic reconnection processes to solar wind and switchback formation.

Findings

CHs show subdued intensity and larger flows in all lines.

Correlations between flows suggest a common origin for solar wind and switchbacks.

Impulsive interchange reconnection explains observed flow patterns and magnetic field rotations.

Abstract

The solar coronal heating in quiet Sun (QS) and coronal holes (CH), including solar wind formation, are intimately tied by magnetic field dynamics. Thus, a detailed comparative study of these regions is needed to understand the underlying physical processes. CHs are known to have subdued intensity and larger blueshifts in the corona. This work investigates the similarities and differences between CHs and QS in the chromosphere using the Mg II h & k, C II lines, and transition region using Si IV line, for regions with identical absolute magnetic flux density (|B|). We find CHs to have subdued intensity in all the ines, with the difference increasing with line formation height and |B|. The chromospheric lines show excess upflows and downflows in CH, while Si IV shows excess upflows (downflows) in CHs (QS), where the flows increase with |B|. We further demonstrate that the upflows (downflows) in Si IV are correlated with both upflows and downflows (only downflows) in the chromospheric lines. CHs (QS) show larger Si IV upflows (downflows) for similar flows in the chromosphere, suggesting a common origin to these flows. These observations may be explained due to impulsive heating via interchange (closed-loop) reconnection in CHs (QS), resulting in bidirectional flows at different heights, due to differences in magnetic field topologies. Finally, the kinked field lines from interchange reconnection may be carried away as magnetic field rotations and observed as switchbacks. Thus, our results suggest a unified picture of solar wind emergence, coronal heating, and near-Sun switchback formation.